Supplementary Table 1: The sentinel hospital IDs and locations. There are 23 hospital sites that perform laboratory confirmation of V. cholerae in Bangladesh.

ID Hospital Division Type
1 District Hospital Norshingdi Dhaka district
2 Adhunik Sadar Hospital Habiganj Sylhet district
3 District Sadar Hospital Cox’s Bazar Chittagong district
4 Adhunik Sadar Hospital Naogaon Rajshahi district
5 General Hospital Patuakhali Barisal tertiary
6 Adhunik Sadar Hospital Thakurgaon Rangpur district
7 District Sadar Hospital Satkhira Khulna district
8 Dhaka Medical College Dhaka Dhaka tertiary
9 Uttara Adhunik Medical College Hospital Dhaka tertiary
10 Bangladesh Institute of Tropical and Infectious Diseases Chittagong Chittagong tertiary
11 General Hospital Tangail Dhaka district
12 General Hospital Narayanganj Dhaka district
13 Sadar Hospital Chuadanga Khulna district
14 General Hospital Meherpur Khulna district
15 General Hospital Comilla Chittagong district
16 Upazila Health Complex Chaugachha Jesssore Khulna subdistrict
17 General Hospital Kusthia Khulna district
18 Upazila Health Complex Madan Mymensingh subdistrict
19 Upazila Health Complex Chhatak Sunamganj Sylhet subdistrict
20 Upazila Health Complex Mathbariya Barisal subdistrict
21 Upazila Health Complex Bakerganj Barisal subdistrict
22 Health Complex Shibganj Rajshahi subdistrict
23 icddr,b Cholera Hospital Dhaka icddrb

Supplementary Table 2: Population living in the cholera surveillance zone.

Buffer (Subdistrict-District-Tertiary-icddr,b in km) Pop Proportion
10-20-30-30 50888584 0.3129697

Supplementary Figure 1: A. Median risk of V. cholerae seroincidence relative to a population-weighted mean by 5 km x 5 km grid cell. These relative risk estimates are bounded such that RRs above and below 2 and -2 were plotted as the values 2 and -2, respectively. The black marks indicate sentinel hospital locations. B. Map of the uncertainty of the seroincidence estimates measured by entropy by 5 km x 5 km grid cell. The black marks indicate the serosurvey sites from the cross-sectional survey conducted in 2015. C. Median number of estimated V. cholerae infections per grid cell in the previous year. The black marks indicate sentinel hospital locations. These estimates were calculated as the product of the median seroincidence risk and 2015 WorldPop population estimate in each grid cell. The black marks indicate sentinel hospital locations.

Figure 1: Cholera greyspots. The 5 km x 5 km grid cells that are colored are cells covered in the cholera surveillance zone. The greyed out grid cells are areas not captured by the national cholera surveillance system in Bangladesh, where we have little information on clinical cases of cholera.

Figure 2: A. Cholera risk map as categorized by the risk of seroincidence relative to a population-weighted mean by 5 km x 5 km grid cell. The map illustrates grid cells of High-Moderate-Low risk and the which grid cells are captured by the cholera surveillance zone (10-20-30-30km for subdistrict, district, and tertiary care, and icddr,b hospitals), indicated by the transparent buffers. B. Cholera risk map as categorized by the estimated number of V. cholerae infections by 5 km x 5 km grid cell. The black marks indicate sentinel hospital locations and the transparent buffers overlayed represent the cholera surveillance zone.

Figure 3: A. Bar plot of the number of people and number of infections in the Bangladesh population and in the cholera surveillance zone living in high-moderate-low risk areas as defined by relative seroincidence risk and absolute number of infections risk measures. B. Bar plot of the percentage of the population and percentage of infection in Bangladesh and the cholera surveillance zone living in high-moderate-low risk areas using the relative seroincidence risk and absolute number of infections as measures of risk.

Supplementary Figure 3:

Supplementary Table 3: Population living in each risk category. The population living in high, moderate, and low risk areas according to relative seroincidence risk across Bangladesh.

Risk Level Population
High 9207436
Moderate 98962248
Low 54429387

Table 1: Part 1. Number and percent infections that may be captured in cholera surveillance zones. The percent infected represents the percentage of infected individuals captured within the cholera surveillance zone out of all infected individuals in Bangladesh. Part 2. Number and percent infections that may be captured in cholera surveillance zones, categorized by relative risk. The infections in surveillance zone represents the percentage of infected people in high-moderate-low risk grid cells among all infections within the cholera surveillance zone. The population in surveillance zone represents the percentage of people living in high-moderate-low risk grid cells among all people within the cholera surveillance zone. The distribution should across risk categories should sum to 100% for each set of buffer sizes. Part 3. Number and percent infections that may be captured in Bangladesh, categorized by relative risk. The captured at-risk population represents the percentage of high-moderate-low risk populations captured by the cholera surveillance zone out of all high-moderate-low risk populations in Bangladesh. The captured infections represents the percentage of infections in high-moderate-low risk grid cells among all infections in high-moderate-low risk grid cells across Bangladesh.

Buffer size Surv. zone pop Number infected % infected in surv. zone pop % of all BGD infections
10-20-30-30 50,888,584 6,802,113 13.4 28.7
Buffer size Risk category Number infected % surv. zone infections Surv. zone pop % BGD pop in surv. zone
10-20-30-30 High 817,295 12.0 3,113,395 6.1
10-20-30-30 Moderate 3,070,442 45.1 19,839,091 39.0
10-20-30-30 Low 2,914,375 42.8 27,936,098 54.9
Buffer size Risk category Surv. zone pop Surv. zone infections Captured At-Risk Pop (%) Captured Infections (%)
10-20-30-30 High 3,113,395 817,295 33.8 32.2
10-20-30-30 Moderate 19,839,091 3,070,442 20.0 20.3
10-20-30-30 Low 27,936,098 2,914,375 51.3 48.2

Supplementary Table 4: Population living in each risk category. The population living in high, moderate, and low risk areas according to the number of infections across Bangladesh.

Risk Level Population
High 98723766
Moderate 54850878
Low 9024426

Table 2: Part 1. Number and percent infections that may be captured in cholera surveillance zones. The percent infected represents the percentage of infected individuals captured within the cholera surveillance zone out of all infected individuals in Bangladesh. Part 2. Number and percent infections that may be captured in cholera surveillance zones, categorized by the number of infections. The infections in surveillance zone represents the percentage of infected people in high/moderate/low risk grid cells among all infections within the cholera surveillance zone. The population in surveillance zone represents the percentage of people living in high/moderate/low risk grid cells among all people within the cholera surveillance zone. The distribution should across risk categories should sum to 100% for each set of buffer sizes. Part 3. Number and percent infections that may be captured in Bangladesh, categorized by the number of individuals infected with V. cholerae . The captured at-risk population represents the percentage of high/moderate/low risk populations captured by the cholera surveillance zone out of all high/moderate/low risk populations in Bangladesh. The captured infections represents the percentage of infections in high/moderate/low risk grid cells among all infections in high/moderate/low risk grid cells across Bangladesh.

Buffer size Surv. zone pop Number infected % infected in surv. zone pop % of all BGD infections
10-20-30-30 50,888,584 6,802,113 13.4 28.7
Buffer size Risk category Number infected % surv. zone infections Surv. zone pop % BGD pop in surv. zone
10-20-30-30 High 5,084,430 74.7 38,491,888 75.6
10-20-30-30 Moderate 1,556,279 22.9 11,266,842 22.1
10-20-30-30 Low 161,404 2.4 1,129,854 2.2
Buffer size Risk category Surv. zone pop Surv. zone infections Captured At-Risk Pop (%) Captured Infections (%)
10-20-30-30 High 38,491,888 5,084,430 39.0 34.9
10-20-30-30 Moderate 11,266,842 1,556,279 20.5 19.9
10-20-30-30 Low 1,129,854 161,404 12.5 12.3

Supplementary Table 5: A. Population living in high certainty areas in the cholera surveillance zone. B. The population living in high, moderate, and low risk areas according to the number of infections across Bangladesh living in areas of high certainty per the entropy threshold of relative seroincidence risk.

Buffer (Subdistrict-District-Tertiary-icddr,b in km) Population Proportion
10-20-30-30 22841377 0.1404767
Risk Level Population
High 0
Moderate 5292801
Low 35316745

Table 3: Part 1. Number and percent infections in grid cells of high certainty that may be captured in cholera surveillance zones. The percent infected represents the percentage of infected individuals captured within the cholera surveillance zone out of all infected individuals living in areas of high predictive certainty in Bangladesh. Part 2. Number and percent infections in areas of high certainty that may be captured in cholera surveillance zones, categorized by relative risk. The infections in surveillance zone represents the percentage of infected people in high-moderate-low risk grid cells among all infections within the cholera surveillance zone. The population in surveillance zone represents the percentage of people living in high-moderate-low risk grid cells among all people within the cholera surveillance zone. The distribution should across risk categories should sum to 100% for each set of buffer sizes. Part 3. Number and percent infections with high predictive certainty that may be captured in Bangladesh, categorized by relative risk. The captured at-risk population represents the percentage of high-moderate-low risk populations captured by the cholera surveillance zone out of all high-moderate-low risk populations in Bangladesh. The captured infections represents the percentage of infections in high-moderate-low risk grid cells among all infections in high-moderate-low risk grid cells across Bangladesh.

Buffer size Surv. zone pop Number infected % infected in surv. zone pop % of all BGD infections
10-20-30-30 22,841,377 2,285,990 10 52.5
Buffer size Risk category Number infected % surv. zone infections Surv. zone pop % BGD pop in surv. zone
10-20-30-30 Moderate 161,827 7.1 1,133,109 5
10-20-30-30 Low 2,124,163 92.9 21,708,268 95
Buffer size Risk category Surv. zone pop Surv. zone infections Captured At-Risk Pop (%) Captured Infections (%)
10-20-30-30 Moderate 1,133,109 161,827 21.4 20.9
10-20-30-30 Low 21,708,268 2,124,163 61.5 59.4

Table 4: A. The population not captured in the surveillance greyspots (cholera surveillance zone). B. The population not captured in the cholera surveillance zone or in areas where we have high certainty of our estimates of relative seroincidence risk. This is also referred to as information greyspots.

Greyspot type Greyspot population Percent in greyspot
Surveillance greyspot 111,710,486 68.7
Greyspot type Greyspot population Percent in greyspot
Information greyspot 98,954,591 60.9